Microporosity in ordered mesoporous aluminosilicates characterized by catalytic probing reactions

The microporosity of ordered mesoporous aluminosilicates assemblied from zeolite nanoclusters is investigated by catalytic reactions with various probing molecules. At first, the samples are treated by bulky basic organic molecular 5,7-dibrom-8-hydroxy-chinolin. In this case, the acidic sites in mesopores are killed, and the acidic sites in micropores that are smaller than the molecular diameter of 5,7-dibrom-8-hydroxy-chinolin are still active. The cracking of 1,3,5-triisopropylbenzene shows that the treated MAS-7 is still catalytically active. In contrast, the treated MAS-9 and treated Al-SBA-15 are almost inactive. These results show that MAS-7 contains micropores whose size is similar to that of beta. Furthermore, the catalytic cracking of cumene shows that the treated MAS-7 and treated MAS-9 are catalytically active but that the treated Al-SBA-15 is inactive. These results show that MAS-9 also contains micropores whose size is similar to that of ZSM-5. Additionally, the catalytic dehydration of 2-propanol (molecular diameter of 3.4 Å) shows that the treated MAS-7, treated MAS-9, and treated Al-SBA-15 are catalytically active. These results suggest that Al-SBA-15 also contains micropores that are larger than 3.4 Å, in good agreement with earlier reports.